The present invention relates to method and apparatus for automatically preparing flexible, disposable packing containers, and more specifically relates to a fully automatic system for winding up an opener cord tightly about the joint between a receptacle and a cover of each packing container which is made of a plastic film and used for encasing together a number of articles such as eggs or fruits.
A packing container of this type in general has a flat box type construction made up of a receptacle and a cover coupled together along an elongated straight joint, and is made from a thermoplastic material such as hard polyvinyl chloride film by vacuum moulding.
After the articles have been placed in the receptacle, the cover is folded over the receptacle along the joint and, conventionally, mating brims of the receptacle and the cover are sealed together by thermal fusion or thermal pressing. In order to open the packing container, it is therefore necessary to break or separate the packing container along the sealed brims and this operation often causes undesirable breakage or damage of the article contained inside.
In order to avoid this problem, a new type of packing container has already been proposed. This new type packing container includes an opener cord tightly winding up the joint between the cover and receptacle of the packing container. For use, the section of the opener cord exposed outside the joint is pulled hard and strongly in order to break the packing container along the joint.
Conventionally preparation of packing containers has been carried out by manual operation. That is, an opener cord in a stretched state has to be wound up and tied by hand about the joint of each packing container. This operation is very time consuming and causes pain on the fingers of the operators. The operation further requires that the operators be skilled. As a result of these factors, it is almost infeasible to prepare packing containers of the foregoing type to meet enlarged consumption of articles on market.